Conventional snorkels which are widely used as diving accessories consist of a mouthpiece and a breathing tube which connects with the mouthpiece. The breathing tube is fastened to the side of underwater goggles or facemasks which are worn on the head. However, depending on the intended use and the degree of skill in said use, various other parts may be added to the above basic construction and many variations in shape or contour are possible. However, such variations involve almost no change in the function of the apparatus. A user inserts the flange portion of the mouthpiece in his mouth and holds the projections of the flange in his teeth. The user then breathes through the breathing opening. The breathing tube is a bent tube formed from soft rubber which is fastened to the mouthpiece and a straight length of tubing extending the bent portion of the tube to above water level. An exhaust portion of the mouthpiece is equipped with an exhaust valve, usually made of rubber and formed in the shape of a thin round dish. The exhaust valve is kept closed by the external water pressure and acts as a check valve which allows the expulsion of breath when the edge portion is opened by the pressure of breath from the inside of the breathing opening. Part of the exhaled breath is also expelled via the breathing tube.
The simplest types of snorkels are not equipped with the exhaust portion of the mouthpiece or the exhaust valve. Accordingly, in this type of snorkel breathing is accomplished exclusively via the bent tube and breathing tube. Thus, during breathing, breath remaining in the bent tube and breathing tube as a result of previous exhalation is re-inhaled.
In such conventional snorkels, breathing can only be accomplished when the upper end of the breathing tube is projecting above water level, which results in a limit to the depth to which the user's head can be submerged. If water enters the breathing tube during use as a result of carelessness or wave action, skill is required in the technique used to expel this water outside of the tube using breath pressure. An inexperienced user may therefore be in danger.